1. Field of the Invention
This invention relates generally to the sucker rod pumping of oil wells, and pertains more particularly to a composite sucker rod and the method of manufacturing such a rod.
2. Description of the Prior Art
Sucker rods have been used for many years in oil well pumping. In this regard, a series of sucker rods, when coupled together, form a string that transmits power from the surface or prime mover apparatus downwardly to the recessed reciprocal pump at the bottom of the well casing.
The American Petroleum Institute has published certain standards and sizes to be adhered to in the manufacture of sucker rods. For instance, the length is specified as being 25 feet. Various rod diameters are also set forth in the API's specifications, as well as other correlated dimensional criteria or data.
In addition, various machining, finishing and allowable tolerances are specified. Still further, while the API refers to, and allows, sucker rods to be produced with an externally threaded pin at one end and an internally threaded box at the other, in actual practice sucker rods with externally threaded pins at both ends are more commonly used in the field, a separate internally threaded coupling being used to connect the various ends of the individual sucker rods into a string of such rods having a length depending upon the depth of the oil well.
In fabricating sucker rods with pins at both ends, it has become common practice to upset the ends of a section of relatively long bar or rod stock to form a bead, a wrench square, a pin shoulder, and an end stub portion of sufficient diameter extending axially from the shoulder so that the threads and neck can be machined thereon to form a finished pin at each end of the completed sucker rod.
Basically, the method that has been heretofore used to make a sucker rod utilizes a number of upsetting steps, the steps being performed sequentially with a set of appropriately configured dies so that the resulting sucker rod has the desired shape at each end. Customarily, seven upsetting steps are performed at one end, and then the seven steps repeated at the other end in order to produce the desired shape. While the rod stock can be initially heated to the proper forging temperature, usually in an induction furnace, the lack of any appreciable mass in the rod stock results in a relatively rapid cooling down of the particular end undergoing the upsetting steps. This has necessitated at least one reheating of the end being worked on in order to complete the upsetting procedure for that end.